Thermostatic control



May 31, 1932. D. WEILL 1,861,288

THERMOSTATIC CONTROL Filed Oct. 25, 1928 2 Sheets-Sheet 2 11 Ila/w y MQW Patented May 31, 1932 PATENT OFFICE LEON DAVID WEILL, or PARIS, FRANCETHERMOSTATIC CONTROL Application filed October 25, 1928, Serial No.315,087, and in Belgium October 28, 1927.

The present invention relates to apparatus for controlling a variablephysical factor and, more especially, that of temperature.

One of the objects of the invention is to provide means operable to heata space to a predetermined temperature and to then cease heating saidspace for a predetermined regulable time.

Other objects will appear in the course of the detailed description nowto be given with reference to the accompanying drawings, in which:

' Figs. 1 and 2 show the temperature control device in diiferentoperating positions. Referring to the various figures of the drawings,there is shown an electrically heated furnace a,-heating resistances 6 bfor said furnace connected to a source of two phase current c,-apyrometer or thermometer (l, provided with a contact or contacts (in thecase of a mercury thermometer, one contact is always submerged-in themercury, and the other, only when the temperature is, sufficiently high),a circuit 7 carrying a relay e in series which is fed with current froma battery or similar small source g,-a lever k controlled by a coreextending into solenoid e and serving to close appropriate switches in acircuit j fed with current from source 0, or, if desired, from anindependent current source,a relay I inserted in circuit and providedwith an arm m serving to open and close a double contact switch ncontrolling the flow of current to a relay 0 adapted to open and close aswitch or circuit breaker i in circuit with source 0 or a partthereof,-a first timing assembly p consisting of a hooked catch 17adapted to engage with a corre sponding element m depending from arm mcarrying switch a (arm m being actuated by arm m through theintermediary of a catch m a regulable timing mechanism p and an arm 2 toLe actuated by timing mechanism p ,and a second timing assembly uadapted to create a delay between the closing of circuit 0 and therelease of element m whereby the inertia in the cooling of furnace a andthermometer d is compensated, and consisting of a regulable timingmechanism u", a hooked arm uadapted to engage with arm 17 and set ofl?timing mechanism u, and arm a adapted to be actuated by mechanism uduring a time interval longer than that during which timing mechanism pfunctions, and a switch 0 adapted to connect relay Z to circuit 70 andthus maintain element m in closed position even after therelease ofelement m The device operates in the following man- As soon as themaximum temperature for which thermometer d is adjusted is reached,current supplied by battery 9 begins to flow in circuit 7, causing relay6 to pull element It downward and close the circuit 7:: leading fromsource 0 to relay Z. The latter exerts a pull on arm m and on arm mthrough the intermediary of catch m bringing double contact switch ninto conductive relation with the leads of circuit 12 and causingcurrent to flow through relay 0 so as to open circuit breaker 8'. Firsttiming mechanism 19 then comes into play to maintain switch 2' open longenough for the furnace to cool through the intermediary of regulabletiming element controlling the length of time catch p continues to pulldownward on element m The opening movement of arms m, m may be effectedby springs, counterweights or equivalent elements opposing the action ofcatch p 30 In the course of operation it may happen that element m isreleased while arm m is still being pulled downward by element 10 thuscausing heating circuit 0 to remain open too long a time. To remedy thisdifficulty, it sufiices merely toreadjust timing mechanism 19?. In casethe furnace lacks sufiicient time to cool means must be provided fortemporarily releasing arm m. This may'be'accomplished by hand by meansof a switch 9 intercalated in circuit j or automatically by means of aswitch adapted to be brought into action by element p as soon as thelatter releases 7 arm m Timing mechanism p may be adjusted so 35 thatarms m, m move away from relay Z at the same time to close switch 0, thelatter occurring as soon as thermometer (1 opens circuit f. Preferably.however, circuit 0 should close somewhat before the release of arm m' tocorrect the heat inertia of the furnace and thermometer. The secondtiming mechanism u is effective to obtain this result and operates inthe following manner: when element oscillates to engage with catch mfirst timing mechanism 2 acts on arm p to raise the latter and set offsecond timing mechanism u through the intermediary of element 'u which,isdrawn upward by 32 Timing mechanism to then acts on element u to drawswitch '0 over into contact with circut k which maintains arm m inclosed position in spite of the fact that circuit a is open. After apredetermined time interval, which is larger than that during whichtiming mechanism. p operates, mechanism u. draws switch '0 back ontocircuit j, the current furnished by 9 stops flowing in circuits 7 and kand arm m is released. In the event that the temperature of the furnacedoes not descend below the maximum value, contact is maintained bythermometer (1 while arm m is released by timing mechanism us action onswitch '0. The catch on arm m, in such a case, will engage with elementm of arm m and relays e and Z, switch n and circuit, breaker 0 willrecommcnce functioning in the manner already described and will repeattheir action until the desired temperature is obtained. If contrariwise,the temperature, as registered by the thermometer, falls below themaximum value before mechanism u has functioned to move switch '0 intocontact with circuit j, the thermometer will cut off the flow of currentin circuit 70, arm m will be released and move upward into position tobe actuated when the temperature again rises above the maximum value.The timing mechanism u may also act, in the same manner as above oncircuit 7 of the thermometer, thus preventing a new interruption for acertain period of the flow of energy from the source to the object awhen circuit a controlled by timing mechanism p, has been closed again.v

If desired, the apparatus may be provided with a signalling system forindicating whether the maximum temperature has been attained or not. Tothis end, a lamp 1' is intercalated in circuit f or inserted in aspecial circuit 8 connected to circuit 0 and arranged to be opened andclosed by arm 72.. Lamp 7' may also serve to calibrate the length oftime that timing mechanism 1) cut heating circuit .0. To regulatemechanism 79. timing mechanism ,u is first temporarily eliminated,thermometer d is adjusted to the maximum temperature desired, andelement p regulated so that arms m, m are released at the end of aninterval, say of 40 seconds, after they have been closed. The furnace isthen heated to the maximum temperature and elements 1", Z and p set inaction. If it is found that lamp 1' remains lighted after mechanism 19releases arm m timer p is readjusted to lengthen the non-heatinginterval. If, contrariwise,

lamp 9" is extinguished before arm m is released, mechanism p isreadjusted toshorten the non-heating period. Once mechanism 1) has beenadjusted, it is easy to set mechanism at to actuate switch '0 for aperiod longer than that during which mechanism p functions.

In the above example the period of the tim-' ing mechanism u, being thesum of the period of timing mechanism p plus a certainlperiod, is longerthan that of said timing mec anism p but it may be understood that ifthe period of mechanism u starts at the end of the period of mechanismp, instead of at the beginning, it must not necessarily be longer.

It will be noted that one of the notable advantages in the presentapparatus is the set ting off of the circuit-breaking mechanismi by asecondary circuit f fed from a battery or other relatively feeblecurrent source. This saves the various contacts and permits a largenumber of makes and breaks to be made without serious deterioration ofthe various moving'and contacting parts.

What I claim is 1. A system of the class ing a main circuit including amain source of electrical energy and a heater operated by said mainsource; a-switch controlling said main circuit; a secondary circuitconnected to said main source and including an electrically responsivedevice controlling the operation of said switch; an auxiliary circuitincluding a thermally'responsive element. an auxiliary source of energyand another electrically responsive device; means operable by said lastmentioned device to control said secfor electrically connecting the sameto said auxlliary circuit for a predetermined period of time.

2. A svstem of the class described comprising a main circuit including amain source of electrical energy and a heater operated by said mainsource: a switch controlling said main circuit; a secondary circuitconnected to said main source and including an electrically responsivedevice controlling the operation of said switch; an auxiliary circuitincluding a thermally responsive element. an auxiliary source of energyand another electrically responsive device: means operable by said lastmentioned device to control said secondary circuit: and a timingmechanism operable by said first mentioned electrically resnonsivedevice for electrically connecting the same to said auxiliary circuitfor a predetermined period of time.

3. A svstem of the class described compris ing a main circuit includinga main source of electrical energy and a heateroperated b said mainsource; a, switch controlling said main circuit; a secondary circuitconnected to described comprisly'responsive device controlling theoperation of said switch; an auxiliary circuit including a thermallyresponsive element; an auxiliary source of energy and anotherelectrically responsive device; means operable by said last mentioneddevice to control said secondary circuit; a first timing mechanismoperable by said first mentioned electrically responsive device tocontrol said switch; and a second timing mechanism operable toelectrically connect said first mentioned electrically responsive deviceto said auxiliary circuit and thereby put the same under the directcontrol of said thermal element for a predetermined period of time.

In testimony whereof I have signed this specification.

LEON DAVID WEILL.

